1. Field of the Invention
This invention relates to an apparatus for the heat treatment of a textile web with a cycled, heated treatment medium which via nozzle boxes and nozzles connected thereto is guided onto the cloth. After impingement on the cloth, the treatment medium goes into a collecting space which is connected to the suction side of a ventilator. The compression side of the ventilator is in communication with a distribution space, whence the treatment medium passes via inlet openings completely or partially into the nozzle boxes or else via inlet openings partially or completely directly back into the collecting space. To this end, there are arranged adjacent to each other an inlet opening leading to the nozzle box and an inlet opening leading to the collecting space, and they are selectively closable to a common register.
2. The Prior Art
With such a device as known from DE-OS No. 33 36 331, it can be achieved that during cloth standstill the treatment medium does not come in contact with the cloth and that, therefore, the treatment medium can be maintained at the set temperature without harm to the cloth. During a stoppage, in fact, the inlet openings through which the treatment medium flows from the distribution space into the nozzle boxes, can be closed by the registers, which in this closed position clear the inlet openings leading to the collecting space. Thereby the treatment medium can be circulated in a short circuit loop, by-passing impingement on the cloth, so that during standstill, overdrying or overfixation of the cloth is avoidable.
In the known apparatus, each inlet opening through which the treatment medium passes partially or wholly directly from the distribution space back into the collecting space, corresponds to the size and form of the inlet opening through which the treatment medium passes from the distribution space into the respective nozzle box. This cross section adaptation of the inlet openings has the disadvantage that with every change of the register position the operating point of the ventilator is changed and, therefore, an optimum mode of operation of the ventilator cannot be maintained. In fact, if the inlet opening leading to the nozzle box is increasingly cleared, the flow resistance caused by the nozzle openings decreases, and it is completely eliminated when the register is in a position which completely closes the inlet opening to the nozzle box. In the short circuit loop, therefore, the ventilator operates against a minimum flow resistance. If, on the other hand, the inlet opening leading to the collecting space is increasingly closed and, consequently, the inlet opening leading to the nozzle box is increasingly cleared, the flow resistance caused by the nozzle openings increases, and it becomes fully effective when the register has assumed a position which completely closes the inlet opening to the collecting space. In normal circulation, therefore, the ventilator operates against a maximum flow resistance.